Mark Hall (The Hawkesbury Institute for the Environment, Western Sydney University)
Agricultural landscapes are everywhere. In fact, they make up approximately 50% of Earth’s habitable land area. That is a lot of land, because we need a lot of food to support our ever-growing human population. But mass-scale food production requires a lot of input – soil, water, fertiliser and, if you are one of 35% of crops (producing fruit, vegetables, nuts), pollinators. Pollination (the transfer of pollen to/from the reproductive parts of flowers) occurs by wind for some species (e.g., many grains), but often animal involvement is required. This could be anything from a bird, butterfly, beetle, fly or small mammal, but often it is done most efficiently by bees. Luckily, we have over 1600 species of native bee in Australia that can do the job.
Agriculture provides some interesting challenges for an ecologist focussed on understanding landscapes, communities and pollinators. While bees likely benefit from abundant floral resources in our managed landscapes—for instance, those offered by mass-flowering crops—they also require other resources, such as suitable nest sites (e.g., in trees for around 30% of species), of which there are fewer in heavily-modified landscapes. The common practice of tilling land for agriculture also likely disrupts or destroys nest sites for the other 70% of Australian bee species that nest in the ground. So, life can be difficult on the land, even for bees! Yet, precious little is known about how robust our bee communities are in these challenging landscapes.
During my PhD, I worked in cropping and grazing landscapes of north-central Victoria to determine whether bee communities differed in streamside vegetation, road margins, scattered paddock trees and productive areas (often containing oats, canola or grazing fodder). I found bees to be fairly abundant in and around farms, most often in the more productive parts of the landscape. This is beneficial for farmers, who are provided with a free pollination service, and enhances our understanding of the ecology of bees so we can better target conservation efforts. However, the most abundant bees tended to be generalist ground-nesting species that feed on many different flower types. Largely missing were the tree-nesting specialist foragers that rely more heavily on native trees and shrubs, such as eucalypts. Researchers from other countries have recorded changes in the diversity and abundance of bees as you move from forest to agricultural and urban areas, so we need to do a lot more work in Australia to make sure we best conserve and protect all of our amazing bee species. Simple measures to address this may be effective, for example, leaving more trees in the landscape, ensuring a diversity of shrub and herbaceous plant species that provide year-round floral resources, and leaving some undisturbed soil. Another important area of focus is working with farmers to modify farming practices, such as pesticide use, which are detrimental to their bee pollinators.
There are also many opportunities to understand and engage with pollinators in agricultural settings. Recently, I have been researching one group of native bees—the stingless bees (Apidae: meliponini)—to understand their pollination potential, husbandry and climatic tolerance. These are wonderful bees. Unlike most species, they live in large colonies (much like the introduced and well-known European honeybee, Apis mellifera), and as such can be kept in man-made hives, provided you live on the tropical and sub-tropical east coast or in northern Australia. These qualities make them ideal candidates for use in agriculture, provided they can be kept healthy and can pollinate the crop of interest well. Through research undertaken by myself and colleagues, we have found these bees to be effective pollinators of crops such as raspberry, strawberry, blueberry, mango and macadamia, and we continue to explore their role in the successful production of many other food crops. But with such management comes great responsibility. Once kept in hives, care is needed to ensure they are able to tolerate environmental conditions, such as extreme heat and cold. In their natural environment, stingless bee species nest in tree cavities, which have greater insulating properties than that of hives. We are currently testing the ability of stingless bee colonies to regulate the internal conditions of different hive types to best protect themselves against heat and cold. This work will aid hive design and husbandry that improves on-farm management. We are also investigating the bees’ thermal tolerance at an individual level, to see what a foragers’ maximum thermal tolerance is. This information will help us determine where and how we can manage these bees for crop pollination now and into the future. The best news is that these bees naturally occur in bushland surrounding farms at a density of approximately 1 colony per hectare. So if you are a grower, consider leaving bushland and other flowering resources around the farm to maximise the free pollination service from stingless bees and all the other wild pollinators out there.
For more information contact Mark here: email@example.com
This article was first published in the ESA Bulletin March 2021.